Geometry preprocessor for generic meshing & SFIA sections

[brookshsmith]

Add native-written preprocessor code which does the following:

• mesh_nodes() meshes ANY section, including dealing with rounded corners. It does assume that nodes are continuous (i.e. it does not handle arbitrary element connectivity). However, this should correctly handle any but built-up sections.
• c_section(), z_section(), and f_section() create and mesh standard C, Z, or F (furring channel) shapes. These functions are entirely unit-agnostic.
• sfia_section() creates a standard SFIA (Steel Framing Industry Association) section, in Imperial inches units. It requires only the designation as a string (e.g. "362S250-54"). Note that the function does not actually look up from a table; it instead generates the section using SFIA rules, so it will accept designations that are not manufactured as well!

All these functions are fully compatible with strip_new(), but will require conversion to old inputs to work with strip().

[github-actions]

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